"Simple," Douken said, a bit of a jokey smirk on his face on him as he answered, "it opens doorways." An odd answer, yes, but it was no normal key the Ancients had left for them to find. Neither did it open gateways to other realms or dimensions. No, it was more that it made its own doors to unlock and open. "I think the main reason why no one has really discovered its secrets is because it involves a magical casting style that has nearly become lost in time thanks to the power of efficiency."
Then they were on the ledge just before the steaming building, Lily was the first to take a dive, holding her dress down so it down flutter so much on the descent. As for Douken, he glanced at his ankles to see if the runes he crafted were still in effect. Sure enough, they did have glow, but was staring to fade. Seemed they were at their last ounce of strength. With this in mind, he hopped wall to wall to ensure a safe descent down back to ground level, the light fading seconds before he landed on ground floor. Sure, that did mean he did stumble upon his landing, but at the very least his legs and ankles were unharmed. Meeting back up with Lily, he gave her a nod, telling her, "Let's go, shall we?" before heading her to the inside of the building.
The interior was of simple design (then again, its hard to challenge the flash Abed's had), but it was effective enough. A simple room hosting a nymph dressed in a simple, yet elegant kimono as a counterwoman and two doors behind her. "Greetings, my new guests," she told them, giving them a like bow, "and welcome to our hot springs. It is a mixed bath, if that is alright with the two of you." He turned over to Lily just to double check, who returned with a smile and a quick, "Sure," as a response. Turning back to the nymph, he nodded as well, as if to signify both parties were fine with it. "Very well. Two guest would be 40 silver then." Paying for the two of them, he handed over the coins, letting her count them before nodding. "The women's changing room is on the left while the men's is on the right. It is up to you whether you wish to keep your towel on or not. However, we would like to ask to keep all personal acts of affections outside of here. Thank you and please enjoy yourselves."
Giving a nod to their hostess, he waved to Lily, telling her, "See you on the other side then," before taking to the men's section, where many baskets were set up to hold the guest's clothing. Stripping down all except for the key around his neck, he placed the items within one of the baskets, wrapping himself in the offered towel before stepping out to the actual hot spring area. "Guess that explains why there was so much steam," he muttered, now seeing it was an outdoor spring, using more or less natural cover to stop others from entering.